1. Field of the Invention
The present invention relates to sheet processing apparatus and image forming system.
2. Description of the Related Art
Conventionally, there is an image forming system that includes an image forming apparatus such as a copying machine or a laser beam printer, and a sheet processing apparatus. Such a sheet processing apparatus takes in a sheet that is discharged after the image forming apparatus forms an image on the sheet and performs a bookbinding process. For example, sheets are folded in the middle or bound approximately at the center of the sheet and folded in two in a bookbinding process.
A conventional image forming apparatus can improve a throughput by shortening the distance between the sheets. For example, there is an image forming apparatus which continuously forms images at predetermined intervals on a continuous sheet in which there is no interval between the sheets that are rolled out from a sheet roll.
Moreover, there is a sheet processing apparatus which performs a process after winding a continuous sheet on which images are formed into a roll (refer to U.S. Pat. No. 5,138,821). Further, there is a sheet processing apparatus that performs a process after stacking the sheets on which images are formed into a z-shaped pattern (refer to U.S. Pat. No. 5,065,992).
FIG. 12 illustrates an example of a conventional sheet processing apparatus which inserts a continuous sheet that is wound into a roll after images are continuously formed on the sheet into envelopes.
Referring to FIG. 12, an envelope roll 34 rolls up open envelopes 58, and three sheet rolls 28 roll up continuous sheets on which images are continuously formed. A cutting unit 40 cuts the continuous sheet. A folding unit 50 folds the sheet cut by the cutting unit 50, an inserting unit 52 inserts sheets folded by the folding unit into the envelopes 58, and a central processing unit (CPU) 54 controls operations of such a sheet processing apparatus.
In a case where the sheet processing apparatus inserts sheets on which images are formed into the open envelopes 58, continuous sheets are each sent out from the three sheet rolls 28 and cut by the cutting unit 40. The folding unit 50 folds the cut sheets, and the inserting unit 52 inserts the folded sheets into the envelopes 58.
The above-described conventional sheet processing apparatus can also cut a continuous sheet that is wrapped around a sheet roll and bind the cut sheets. However, it takes time to cut the sheets one by one from a continuous sheet and stack the sheets again to bind the sheets. Moreover, such a sheet processing apparatus needs a stapling unit, a double folding unit, and a cutting unit which cuts edges of a double folded sheet bundle instead of the inserting unit 52.
A sheet processing apparatus which includes a stapling unit, a double folding unit, and a cutting unit as described above can perform a binding process. However, since a double folding process, a stapling process, and a cutting process are separate processes, the binding process takes a long time, and productivity decreases. Further, an amount of cutting wastage and consumption of the sheet roll increase if a cutting amount of edges of a double folded sheet bundle increases.